This invention relates to the repair of alloy articles and, more specifically, to a filler alloy composition for use in gas-tungsten-arc-welding (GTAW) or plasma-arc-welding (PAW) of cast gas turbine component alloys.
There are numerous cobalt based alloys used in both the manufacture and repair of high-temperature operating gas turbine engine components including combustors, turbine vanes, nozzles, etc.
Representative examples of cobalt base alloys for the production and/or repair of superalloy articles are disclosed in U.S. Pat. Nos. 4,830,934; 4,614,296; 4,396,577; 4,381,944; 4,285,459; 4,058,415; 3,355,287; 3,276,865; 3,271,140; and 3,260,505.
The principal method of repairing cast gas turbine nozzles which have experienced various forms of damage during many hours of service is that of GTAW or PAW deposition of a suitable filler alloy. Service-induced cracks, corrosion or foreign object damage are typically removed by grinding as a preparation for filler alloy deposition. In order to provide a maximum service-life repair interval, the filler alloy should exhibit tensile, rupture and fatigue strength as well as ductility comparable to the parent alloy, i.e., the article alloy being repaired. An equally important criteria is that the oxidation and hot corrosion (or sulfidation) resistance of the filler alloy be equivalent to, or at least closely approximate the parent alloy.
Two commercially available filler weld alloys for use in GTAW repairs of a cobalt-base parent alloy have compositions (by weight) as follows: